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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 31, issue 8
Ann. Geophys., 31, 1285–1295, 2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 31, 1285–1295, 2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 01 Aug 2013

Regular paper | 01 Aug 2013

A study of solar and interplanetary parameters of CMEs causing major geomagnetic storms during SC 23

C. Oprea1, M. Mierla1,2,3, D. Beşliu-Ionescu1,4, O. Stere1, and G. Mariş Muntean1 C. Oprea et al.
  • 1Institute of Geodynamics of the Romanian Academy, 19–21 Jean-Louis Calderon, Bucharest, Romania
  • 2Research Center for Atomic Physics and Astrophysics, Faculty of Physics, University of Bucharest, Romania
  • 3Royal Observatory of Belgium, Brussels, Belgium
  • 4MoCA, School of Mathematical Sciences, Monash University, Clayton, Victoria 3800, Australia

Abstract. In this paper we analyse 25 Earth-directed and strongly geoeffective interplanetary coronal mass ejections (ICMEs) which occurred during solar cycle 23, using data provided by instruments on SOHO (Solar and Heliospheric Observatory), ACE (Advanced Composition Explorer) and geomagnetic stations. We also examine the in situ parameters, the energy transfer into magnetosphere, and the geomagnetic indexes. We compare observed travel times with those calculated by observed speeds projected into the plane of the sky and de-projected by a simple model. The best fit was found with the projected speeds. No correlation was found between the importance of a flare and the geomagnetic Dst (disturbance storm time) index. By comparing the in situ parameters with the Dst index we find a strong connection between some of these parameters (such as Bz, Bs · V and the energy transfer into the magnetosphere) with the strength of the geomagnetic storm. No correlation was found with proton density and plasma temperature. A superposed epoch analysis revealed a strong dependence of the Dst index on the southward component of interplanetary magnetic field, Bz, and to the Akasofu coupling function, which evaluates the energy transfer between the ICME and the magnetosphere. The analysis also showed that the geomagnetic field at higher latitudes is disturbed before the field around the Earth's equator.

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